Field of Invention
The present invention relates to a method for ring-spinning, and more particularly to a method and apparatus for pneumatic guiding and capturing strand fibers, wherein a pneumatic apparatus is installed on existing ring frame to improve ring-spun yarn quality, which belongs to a technical field of textiles.
Description of Related Arts
Hairiness is one of the important indexes of yarn quality. Yarn hairiness not only influences efficiency of post-process such as weaving and knitting, but also influences appearance and quality of the final product. Especially, because high-speed shuttleless loom is widely used conventionally, it is quite important to reduce the yarn hairiness.
The yarn hairiness is generated during ring-spinning process. The key problem thereof lies in that: front roller nip presses the fiber strand into a flat shape, and by a twisting torsion force, internal fibers of the flat fiber strand move outwardly. When a certain part of the fiber goes inside the yarn through internal-external migration, the fiber end protruding from the spinning strand is not able to be twisted onto the yarn after being separated from the roller nip, resulting in hairiness. When a fiber is located at the most edge of the flat fiber strand, the cohesion force between the fiber and the spinning strand is weak, and the fiber just moves out of the front roller nip. Under this situation, the fiber is easy to be changed in direction by negative pressure of a pipe, and be separated from the spinning strand. At this time, the fiber is completely separated from the front roller nip and is sucked away by the negative pressure of the pipe, resulting in dropping fiber, and decreasing of fiber utilization as well as ring-spun yarn quality.
To solve the problems of excessive hairiness and poor quality of spun yarn during ring-spinning, scholars over the world have researched a lot. Two methods are mainly used. One is using the conventional method for optimization of conventional ring-spinning process. The method is able to reduce yarn hairiness to some extent, but the effect is limited. The other one is using new spinning technology or special hairiness-eliminating apparatus to eliminate hairiness and drastically improve ring-spinning quality. The new ring-spinning technology or special hairiness-eliminating apparatus is a hot spot of ring-spinning technology. Conventionally, compact spinning technology is a represent of the new ring-spinning technology, such as U.S. patent “Apparatus for stretching, condensing and transporting a rove of fibers during a spinning operation”, published in Dec. 18, 1984, U.S. Pat. No. 4,488,379; U.S. patent “Apparatus for condensing a drafted fiber strand”, published in Jun. 13, 2000, U.S. Pat. No. 6,073,314; U.S. patent “Arrangement for condensing a drafted fiber strand”, published in Jul. 4, 2000, U.S. Pat. No. 6,082,089; U.S. patent “Transport belt for transporting a fiber strand to be condensed”, published in Jan. 9, 2001, U.S. Pat. No. 6,170,126B1; U.S. patent “Arrangement and method for condensing a drafted fiber strand and method for making yarn therefrom”, published in Jul. 24, 2001, U.S. Pat. No. 6,263,656B1; U.S. patent “Apparatus for condensing a drafted strand”, published in Aug. 14, 2001, U.S. Pat. No. 6,272,834B1; and U.S. patent “Condensing zone for a spinning machine”, published in May 29, 2001, U.S. Pat. No. 6,237,317B1. Key principles of the aforementioned patents about compact spinning technology are for ring-spinning, wherein flat ribbon-like fiber strands are condensed to eliminate spinning triangular zone, increase the cohesion force between edge fibers and the spinning strand, strengthen the controlling of the edge fiber of the ribbon-like strand, effectively reduce exposed and escaped fiber ends during spinning, reduce yarn hairiness and fiber loss, and inhibit flyings. However, during eliminating of the spinning triangular zone by compact spinning, fiber migration of the spun yarn inner structure is not enough, and the yarn internal fibers are arranged too straight and compact, resulting in too large stiffness of yarn and serious deterioration of softness. In particular, compact spinning technology using airflow to condense fiber strand requires additional negative pressure vacuum equipments to increase energy consumption, leading to high costs of the compact spinning technology in installation, operation and maintenance, and becoming expensive spinning, which is contrary to the concept of energy saving and low carbon production.
Conventionally, the special hairiness reducing apparatus is air-jet style, and is installed between the front roller nip and the pigtail guider. By additional vortex airflow, the formed hairs are loosely wrapped onto the yarn surface, such as U.S. patent “method and apparatus yarn treatment”, published in Apr. 10, 1979, U.S. Pat. No. 4,148,779; and U.S. patent “method and apparatus for modifying spun textile yarn”, published in Aug. 22, 1989, U.S. Pat. No. 5,263,311. Main differences between the above patents lay in that due to difference of jet apparatus; force directions on surface fibers of the yarn are different, resulting in different wrapping effects and different hairiness-eliminating effects. However, the apparatus are only able to be installed behind the twisting triangle zone (due to the fibers in twisting triangle area are loose fibrous, and jet flow will lead to confusion motion of the fibers, which will cause end-breakage during spinning), targets of the jet flow are yarn and surface hairiness. Rotating effects on the targets caused by the jet flow are different, for simply fitting or loosely wrapping the hairs onto the yarn surface. As a result, in the subsequent processes (such as winding), all the loosely wrapped hairiness protrudes the yarn surface again due to the mechanical friction pulling fiber ends out of the yarn surface structure, which means that hairiness is not truly eliminated. Furthermore, the above special hairiness reducing apparatus are not able to solve a key problem that strand edge fibers are easy to escape, which forms fiber droppings and flyings.
Chinese patent “Ironing-spinning method for improving yarn properties”, published in Jul. 11, 2007, patent number 200610166509.9; and U.S. patent “Method and apparatus for producing high quality yarn on a ring frame”, published in Jun. 30, 2009, U.S. Pat. No. 7,552,580B2 both provide ironing-spinning methods for heating the fiber in the spinning triangle zone to improve the yarn quality. However, ironing apparatus of the methods are only applicable to lower fiber modulus for improving fiber torsion and bending performance, and improving yarn surface smoothness as the fibers become soft enough to be spun into the yarn by twisting force during spinning. However, the key problem that edge fibers of the flat ribbon-like fiber strand are easy to escape, which forms fiber droppings and flyings, cannot be solved by this method and apparatus. Furthermore, the ironing apparatus also has extra energy consumption, and has poor effects on the fibers with poor heating sensitivity (such as wool fiber). Therefore, yarn quality is not improved for wool fibers.